Alas, as with so many of these 'claims' on FB, actual data is missing.
And in this case, the lack of units does not help either. How can you compare paper with beef? What is 'saving a tree'?

My guess is that the underlying statement is 3432 trees are felled for one year of beef consumption. I don't dispute that eating meat has a large environmental impact, but can anyone explain this number (and prove my assumption - because alternatives are possible*)?

I don't have the time to research an answer, but it also seems to be assuming the choice is between eating beef or eating nothing. I would assume the equivalent nutritional value in plants would use up more land than beef would.
– EthanMay 9 '16 at 15:46

@Ethan On the one hand, bovine need to eat plants which adds a step of inefficiency relative to eating plants directly. On the other hand, bovine can eat grasses that humans can't. So in a place where you would need to cut down trees to grow other plants, growing plants that humans can directly eat would be more efficient, but in a grass ecosystem with native bovine present, eating a sustainable fraction of the bovine would be very environmentally friendly. Also, cattle can eat left over portions of grain plants (straw) that humans don't eat.
– DavePhDMay 9 '16 at 16:13

@DavePHD: Cattle also aren't eating only one harvest before being butchered. A cow is built up over (according to one of the answers) 2 years. It's possible that because of this, it can continuously eat grass from the same area before going onto my plate, increasing space efficiency to some degree. Your answer is already sufficient for the question, but that analysis would still be interesting.
– EthanMay 9 '16 at 16:20

Tree density varies, and we used an average of 700 trees per acre (this number was taken from DOE’s "Sector-Specific Issues and Reporting Methodologies Supporting the General Guidelines for the Voluntary Reporting of Greenhouse Gases under Sections 1605(b) of the Energy Policy Act of 1992")

(Even 700 trees per acre is a very high estimate. See the recent Nature article Mapping tree density at a global scale, Fig. 3, that shows that depending upon the type of ecosystem tree density varies from 200 to 1000 per hectare, or 80 to 400 per acre)

700 trees per 43560 square feet is 1 tree per 62 square feet.

So even assuming that all cattle graze on land which was previously forested (rather than the Great Plains of North America which were naturally grasslands with millions of bison), the cartoon is off by a huge factor on the number of trees per acre (trees per pound of beef).

The next major problem with the cartoon (as PhillS is commenting) is more subtle, but also very severe. The time for trees to grow to make paper is 25-40 years. So, when comparing to using trees for paper, it doesn't make sense to count the acreage (square footage) as if 700 trees could grow on one acre in one year.

In 1630, the estimated area of U.S. forest land was
1,023 million acres or about 46 percent of the total
land area. Since 1630, about 256 million acres of forest
land have been converted to other uses—mainly
agricultural.

So if everyone in the United States just killed themselves, and let the full 256 million acres of forest lost regrow, this would be 256 million acres per 323 million people or 0.79 acres per person. With 700 trees per acre, 555 would be saved per person. Not 555 trees per year, but 555 trees per lifetime of a tree.

Furthermore, according to the Nature article cited above, globally there is a:

gross loss of approximately 15.3 billion trees on an annual basis

This is about 2 trees per person per year. So stopping all deforestation for all reasons (not just beef, not just all meat, but all human activity) would save 2 trees per person per year.

Is there any clue as to how that first reference arrives at "1 lb of beef = 55 square feet of forest"? That calculation itself is not clear. Also, it should be noted that, using this number, 3432 trees equals 62 pounds of beef in a year; this works out to nearly five quarter-pounders a week. That seems like a very high estimate, though since the rest of the numbers in the claim also seem... arbitrary... I might be reading too deeply.
– iamnotmaynardMay 6 '16 at 14:17

26

@iamnotmaynard, "this works out to nearly five quarter-pounders a week. That seems like a very high estimate" You ain't from around here, are ya boy?
– KevinMay 6 '16 at 14:22

1

However, in line with Andrew Grimm's comment, I've usually heard that the deforestation occurs in South America (mainly Brazil), which could have a far different tree density that in the U.S.
– iamnotmaynardMay 6 '16 at 14:22

45 trees per 55 square feet would leave only 1.22 square feet for each tree, which is obviously silly. However, 45 trees in a square area 55 ft on each side (i.e. 3025 square feet) works out to one tree per 67 square feet, which is well within the range of your estimates. I wonder if that's where the mistake came from originally.
– NathanielMay 8 '16 at 15:29

The claim really originates from 1986, and over the years has been stripped down to a factoid, to fulfill Bradbury's prophecy "Films and radios, magazines, books leveled down to a sort of pastepudding norm".

It started from the editorial Our steak in the jungleBioScience (November, 1986), page 642 on the effect of Central American beef production on tropical forests, and is quoted and referenced in many subsequent documents.

Quoting from the editorial:

But what would the consumption of a typical four-ounce hamburger represent in terms of pounds or square feet of tropical forest? A well-developed acre of Central American rain forest has about 800,000 pounds of plants and animals. After forest removal and pasture establishment, the cattle will gain about 50 pounds per acre per year, or 400 pounds during the eight-year lifetime of a typical pasture. Because about half the animal is composed of skin, bones, and other nonfood portions, the total beef production is 200 pounds (800 four-ounce hamburgers). Dividing the 800,000 pounds of forest life per acre by 800, the number of hamburgers produced during the lifetime of a one-acre pasture reveals that we "lose" about half a ton of forest for every hamburger produced in Central American forest. Considering the tradeoff in terms of area (43,793 square feet per acre divided by 800 hamburgers) reveals that each Central American forest hamburger represents about 55 square feet of forest — roughly the size of a small kitchen.

What life might inhabit the 55 square feet of tropical forest represented by a single hamburger? Such a space could contain one vigorous tree, 60 feet tall and weighing about 875 pounds. Below the tree might be some 50 saplings and seedlings in some 20—30 different species (another 120 pounds). Living in the vegetation would be thousands of insects in more than a hundred species (as much as 2 pounds). Several of these insects would likely belong to species not yet known to science. Dozens of bird, reptile, and mammal species would regularly pass through and use this patch of forest (2 pounds). Finally, an almost unimaginable diversity and abundance of mosses, fungi, and microorganisms would be associated with leaf surfaces, bark, roots, and the soil (1 pound). All told, millions of individuals and thousands of species, inhabit that patch of tropical forest represented by a single hamburger.

So the area "55 square feet" appears in this article and it is said that one tree and "50 saplings and seedlings" might be in this area.

Much more recently, Emily Moran Barwick of "Bite Size Vegan" created a video the REALLY Inconvinent Truth. In the video and accompanying text, the same 55 square feet is used, but now applied to one pound of beef and it is stated that "45-55" trees are in this area. Quoting Emily's text:

the average us citizen eats 185 pounds of meat every year, and 62.4 pounds of beef...to produce 1 pound of beef, it takes approximately 55ft.² of rain forest, which depending on the area, is anywhere between 45 and 55 trees. so if you didn’t use any paper at all for an entire year, you’d be saving at most 8.51 trees. whereas if you avoid just 1 pound of beef, you’re saving 45 to 55 trees. now if you went an entire year without eating any beef, you’d be saving 3,432 trees.

Looking back at the 1986 article, if you consider trees from the moment of germination, 51 trees (1 mature tree plus 50 saplings and seedlings) are said to be in the area. However, the video specifically mentions 40 foot trees in arriving at the number for paper. Furthermore, according to Mapping tree density at a global scaleNature 525, 201–205 (10 September 2015), "almost all of the collected data sources...define a tree as a plant with woody stems larger than 10 cm diameter at breast height". So considering saplings and seeding when counting trees is not standard practice.

Emily takes 62.4 pounds of beef per US person per year and multiplies that by 55 trees, obtaining 3432 trees per year.

@Jason It doesn't become 7.5 lbs. You are assuming all the beef is imported, when in fact the US is the biggest producer of beef in the word. Less than 1 pound per person is imported annually from South America. (The 1986 article isn't about South America though, it's really about Costa Rica, which is North America, but even less is from there).
– DavePhDMay 9 '16 at 14:45

2

You are correct, the truth is even further from the stated figures.
– JasonMay 9 '16 at 15:03